This project is an F32 postdoctoral fellowship designed to enhance the candidate's training in the application of stable isotope tracer techniques to measure metabolic flux. Hepatic insulin resistance results in inappropriately elevated gluconeogenesis in the liver and activation of certain pathways of the hepatic TCA cycle. These effects contribute to diabetes by increasing blood glucose and also perhaps interact with liver disease by impinging on oxidative metabolism. The TCA cycle is a central pathway of both gluconeogenesis and hepatic energy metabolism. It is located in mitochondria and provides energy through its oxidative function and intermediates required for gluconeogenesis, fatty acid synthesis, and amino acid production through its anaplerotic function. Impaired mitochondrial function has been linked to hepatic insulin resistance. Recent results from our laboratory have shown that hepatic insulin resistance stimulates both anaplerosis and oxidative metabolism in the TCA cycle. Whether increased TCA cycle flux is a cause or an effect of increased gluconeogenesis remains unknown. To address this question, we will specifically disrupt the oxidative function and anaplerotic function of the TCA cycle using conditional mouse genetics. The role of these two pathways will be examined using a combination of stable isotope tracer-based nuclear magnetic resonance and mass spectrometry techniques to measure metabolic flux. The necessity of these pathways for hepatic insulin resistance will be tested in normal and high fat diets. We hypothesize that disrupting the anaplerotic or oxidative function of the TCA cycle will reduce hepatic gluconeogenesis and therefore reduce the severity of hepatic insulin resistance. These studies will serve as a scaffold for the candidate to train in the application of metabolic flux approaches.
Obesity causes changes in liver function that contribute to the development of diabetes. We plan to use advanced biochemical techniques to study how specific aspects of metabolism in the liver might cause these changes. This work will provide better understanding of the causes of diabetes and may contribute to diabetes prevention efforts.
